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Rate adaptive pacemaker using impedance measurements and stroke volume calculations

a rate adaptive pacemaker and impedance measurement technology, applied in the field of rate adaptive pacemakers, can solve the problems of heart failure, lack of oxygen supply to the myocardium, and inability to meet the physiological needs of the patient's organism, and achieve the effect of pacing ra

Inactive Publication Date: 2005-12-13
ST JUDE MEDICAL
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  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Benefits of technology

[0007]An object of the present invention is to provide a rate adaptive pacemaker in which the pacing rate is prevented from becoming too low, such that the above discussed inconveniences for the patient are avoided.
[0009]Thus, by satisfying two predetermined relations the pacemaker according to the invention ensures a sufficient minimum energy supply to the patient's organism or body and at the same time the maximum value of the stroke volume is limited and these conditions are continuously automatically checked.

Problems solved by technology

The pacing rate of a rate adaptive pacemaker may become too low due to the physical demand of the patient's organism and heart.
This may result in lack of oxygen supply to the myocardium.
Under certain conditions the heart may not be able to fulfil the physiological needs of the patient's organism and heart if the pacing rate is not limited.
Thus, a pacing rate that is too low may cause an influx of blood enriched with oxygen that also is too low.

Method used

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  • Rate adaptive pacemaker using impedance measurements and stroke volume calculations
  • Rate adaptive pacemaker using impedance measurements and stroke volume calculations

Examples

Experimental program
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Embodiment Construction

[0015]To avoid the current cardiac output CO

CO=SV×HR  (5)

becomes lower than the rest state cardiac output COrest the pacing rate must be above a lower pacing rate limit given by

lower pacing rate limit=(Corest) / (SV)  (6)

and since

COrest=HRrest×Svrest  (7)

lower pacing rate limit=(HRrest)×(Svrest / SV)  (8)

[0016]In addition the maximum value of the stroke volume must be limited, i.e.

SV<L×Svrest  (9)

[0017]Thus, the following two conditions must be fulfilled simultaneously for insuring a physiologically well founded heart work management at low work loads.

Pacing rate limit>(HRrest)×(Svrest / SV)  (10)

SV / SVrest<L  (11)

where L is a constant typically equal to a value of 1.2 to 1.5, depending on the health of the patient's myocardium.

[0018]Thus the lower pacing rate limit is continuously automatically calculated from the measured actual stroke volume SV and known values of SVrest, HRrest and the constant L. The actual stroke volume can be determined from e.g. bioimpedance measurements as w...

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Abstract

A rate adaptive pacemaker comprises a means (2) for determining the demand of the patient's organism, a pacing rate controlling means (16) for controlling the pacing rate in response to the patient's demand, and a pacing rate limiting means (20) for preventing the pacing rate from becoming too low. The pacing rate limiting means is adapted to limit the pacing rate downwards such that a first predetermined relation is satisfied between actual cardiac output (CO) and cardiac output (COrest) for the patient in rest conditions and a second predetermined relation is satisfied between actual stroke volume (SV) and rest stroke volume (SVrest).

Description

BACKGROUND OF THE INVENTION[0001]1. Field of the Invention[0002]The present invention relates to a rate adaptive pacemaker of the type having an arrangement for determining the demand of the patient's organism, a pacing rate control for controlling the pacing rate in response to the patient's demand, and a pacing rate limiter for preventing the pacing rate from becoming too low.[0003]2. Description of the Prior Art[0004]The pacing rate of a rate adaptive pacemaker may become too low due to the physical demand of the patient's organism and heart. This may result in lack of oxygen supply to the myocardium. Under certain conditions the heart may not be able to fulfil the physiological needs of the patient's organism and heart if the pacing rate is not limited.[0005]It is known to set a lower limit for the pacing rate. This limit value is normally determined from the patient's diagnosis and a constant or externally programmable limit can be set. Thus U.S. Pat. No. 4,535,774 describes a ...

Claims

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Application Information

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IPC IPC(8): A61N1/365
CPCA61N1/36585
Inventor MIN, MARTKINK, ANDRESPARVE, TOOMAS
Owner ST JUDE MEDICAL
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